Polyethylene terephthalate injection blow molding

Polyethylene terephthalate is injection blow molded to make water and carbonated drink bottles, and other liquid food packages. High stiffness, excellent clarity, and good resistance to carbon dioxide permeation are the principal attributes of these bottles. We carefully control molding conditions to promote transparency and surface gloss, which are prized for food... 

Multilayer injection blow-molded containers have been available for a much shorter time than multilayer extrusion blow-molded containers, as development of the process was more difficult. However, these too are now available. A prominent example is multilayer polyethylene terephthalate (PET)-based ketchup bottles, which contain three layers of PET, and two layers of ethylene vinyl alcohol (EVOH) as an oxygen barrier. 

Applicable materials for the injection blow molding process include high-density polyethylene (HOPE), low-density polyethylene (LDPE), polystyrene (PS), styrene acrylonitrile (SAN), ethylene vinyl acetate (EVA), polypropylene (PP), polycarbonate (PC), and polyurethane (PU). Polyethylene terephthalate (PET) and polyacrylonitrile (PAN) are less commonly used in the injection blow molding processes. 

Polyethylene terephthalate is most often extruded into films or fibers, or blow molded into bottles. Polybutylene terephthalate is primarily found in injection molded parts. Such parts are highly crystalline, which makes them opaque. Polybutylene terephthalate is often modified with glass fibers or impact modifiers. Table 24.1 contains applications by processing method and resin. 

Polyesters exhibit excellent high temperature strength and electrical properties making them a good choice for many demanding applications. They also are physiologically inert allowing them to be used in food contact applications. The two common polyesters, polyethylene terephthalate and polybutylene terephthalate, are both used in injection molded products. Polyethylene terephthalate is often used in both extrusion and blow molded processes also. 

Thennoset polyesters, such as Glyptal, alkyds and glass reinforced unsaturated polyesters have been available for several decades but Injection moldable polyaryl esters are relatively new. Whinfield and Dickerson extruded polyethylene terephthalate (PET) fibers (Dacron) in the 194O s. ( )pET was also extruded as film (Mylar) in the 1950 s but this polymer was not blow molded commercially until the 1970 s. 

Polyethylene terephthalate (PET, polyethylene glycol terephthalate) n. A saturated, thermoplastic polyester resin made by condensing ethylene glycol, and terephthalic acid, used for textile fibers, water-clear, biaxially oriented film (e.g., Mylar ) and, more recently, for extruded, thermoform-able sheet (TV-dinner trays), injection-molded parts, and large, blow-molded, soft-drink bottles. It is extremely hard, wear- and chemical-resistant, dimensionally stable, and has good dielectric properties. See also polyester, saturated and crystallized polyethylene terephthalate (See image). 

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